The present invention relates to a method and an apparatus for detecting blood vessels from video images generated by a B mode ultrasound scan of subcutaneous blood vessels and for displaying an enhanced video image highlighting the vascular walls on the video images obtained from the ultrasound scan.
Generally, B mode scans are utilized to view anatomical structures in a plane generally perpendicular to the surface of the skin. However, the typical ultrasound scan is presented to the physician or operator as a black and white image, i.e., a gray scale image. The quality of the image is poor, especially if the subcutaneous vascular structure is displayed in real time, because of the large amount of back scatter from both the vascular system and the surrounding tissue.
U.S. Pat. No. 4,812,622 to Pennypacker et al. discloses an infrared imager for viewing subcutaneous blood vessels. The system compensates for horizontal sweep of the NTSC video image to even the image background. The system also averages horizontal lines for vertical image uniformity. Further, the Pennypacker et al. system amplifies the video image to obtain a high contrast enhancement of the image. A logarithmic format is utilized in the system. U.S. Pat. No. 4,720,871 to Chambers discloses digital image convolution. U.S. Pat. No. 4,437,161 to Anderson discloses a medical imaging apparatus which obtains a video signal from an x-ray detector. A difference signal is obtained by subtracting a reference image signal from a second individual image signal. If the difference exceeds a threshold, a change image signal is generated. U.S. Pat. No. 4,802,002 to Plut et al. discloses a medical diagnostic television imaging system at the X-ray source, an image-intensifier tube and a video camera. Circuitry is provided for suppressing delivery of certain video images to the monitor in response to selection of one of the plurality of scan rates. U.S. Pat. No. 4,737,842 to Nagasaki discloses a color-emphasis circuit for color endoscope. The system modulates color signals, averages the color signals and detects hue differences between the modulated color signal and the modulated averaged signal. A hue difference changer is provided for widening the detected hue difference. U.S. Pat. No. 4,841,360 to Bergmeir discloses an apparatus for reproducing colored originals with an additional gray scale balance and/or color contrast adjustments. U.S. Pat. No. 4,742,388 to Cooper et al. discloses a color video endoscope system with an electronic color filtering. The endoscope senses sequential fields of red, green and blue light reflected from a patient. U.S. Pat. No. 4,831,437 to Nishioka et al. discloses a system with color balance adjusting mechanism. U.S. Pat. No. 4,805,016 to Kato discloses another endoscopic system.
U.S. Pat. No. 4,170,987 to Anselmo et al. discloses a medical diagnosis system sensing various wavelengths of light reflected from a patient. U.S. Pat. No. 4,751,643 to Lorensen et al. discloses a system for processing nuclear magnetic resonant signals. U.S. Pat. No. 4,754,332 to Bergquist discloses a device for presenting and selectively altering the brightness of a digitized image. U.S. Pat. No. 4,823,194 to Mishima et al. discloses a method for processing gray scale images.
U.S. Pat. No. 4,199,748 to Bacus discloses a system for identifying characteristics of red blood cells. U.S. Pat. No. 4,731,743 to Blancato discloses a system for analyzing hair styles. U.S. Pat. No. 4,812,909 to Yokobayashi et al. discloses a cell classification system.
One prior art system senses blood flow utilizing Doppler principles and a specially configured ultrasound scanner. Soundwaves from the ultrasound scanner are presented in a phased array and electronic circuitry connected to the scanner senses a Doppler shift in the return signals. This system is called a Quantum QAD-PV Angiodynography Imaging System sold by Quantum Medical Systems, Inc. of Issaquah, Wash. Blood flow through blood vessels is detected by the Doppler shift in the signals and the system color enhances the generally black and white or gray scale video image produced by the scanner. The blood flowing through the vessels is displayed in red whereas the background, that is the surrounding tissue, is displayed in black and white.